Method and apparatus for rate shaping injection in a hydraulically-actuated electronically controlled fuel injector

Abstract

A hydraulically-actuated electronically-controlled fuel injection system includes a solenoid operated main valve that controls the flow of actuating fluid to the individual injectors. The flow of pressurized actuating fluid pressurizes the fuel and causes injection to occur. The present invention accomplishes pilot injection and/or other injection rate shaping by constricting the flow of pressurized actuating fluid to the piston pump chamber of the individual injectors during a portion of each injection cycle. Constricting the flow of pressurized actuating fluid is accomplished by a separately controlled solenoid valve preferably positioned between the actuating fluid manifold and the main control valves of each individual injector.

I claim: 
     
       1. A hydraulically-actuated electronically-controlled fuel injection system comprising: a manifold holding an amount of a pressurized actuating fluid therein;   a plurality of hydraulically-actuated fuel injectors, each having an actuator valve assembly and a piston pump chamber adjacent an intensifier piston;   a branch passage extending between said manifold and said piston pump chamber of each of said injectors; and   means for individually alternating each of said branch passages between a first condition and a second condition, said branch passage permitting free flow of actuating fluid between said manifold and said piston pump chamber when in said first condition but permitting only constricted flow of said actuating fluid between said manifold and said piston pump chamber when in said second condition.   
     
     
       2. The hydraulically-actuated electronically-controlled fuel injection system of claim 1, wherein said means for individually alternating includes an electronically operated valve positioned in each of said branch passages. 
     
     
       3. The hydraulically actuated fuel injection system of claim 2, wherein each of said branch passages includes a pilot line with a small diameter and a main line with a large diameter; and said electronically operated valve is positioned to alternate said main line between being open and closed.   
     
     
       4. The hydraulically actuated fuel injection system of claim 3, wherein said large diameter is at least three times larger than said small diameter. 
     
     
       5. The hydraulically actuated fuel injection system of claim 2, wherein said means for individually alternating further includes an electronic control module in communication with said electronically operated valve and a plurality of operating condition sensors, and said electronic control module being capable of controlling said electronically operated valve. 
     
     
       6. The hydraulically actuated fuel injection system of claim 5, wherein said electronic control module includes an amount of accessible memory; a plurality of electronic valve control signals are stored in said memory; and   each of said electronic valve control signals corresponds to a particular operating condition.   
     
     
       7. The hydraulically actuated fuel injection system of claim 2, wherein said electronically operated valve is a constriction valve mounted in each of said branch passages, said constriction valve having a first open condition and a second constricted condition. 
     
     
       8. The hydraulically actuated fuel injection system of claim 7, wherein the flow area through each of said branch passages is at least ten times larger when said constriction valve is in said first open condition than when said constriction valve is in said second constricted condition. 
     
     
       9. A method of rate shaping injection in a hydraulically-actuated electronically-controlled fuel injector system that includes an actuator valve assembly and a piston pump chamber connected via a branch passage to a source of pressurized actuating fluid, the method comprising the steps of: opening the actuator valve assembly for an amount of time during each injection cycle; and   constricting the flow of actuating fluid through a branch passage over a portion of said amount of time.   
     
     
       10. The method of claim 9 wherein the engine system has a number of operating conditions and the method further comprises the steps of: predetermining a desired set of times that include a main control on-time, a main control off-time, a constriction on-time and a constriction off-time for a plurality of engine system operating conditions;   storing the predetermined sets of times in a memory location;   determining the operating condition of the engine system;   retreiving a set of times from the memory location corresponding to the engine system operating condition;   activating the actuator valve assembly at the main control on-time;   unconstricting the branch passage at the constriction off-time;   deactivating the actuator valve assembly at the main control off-time; and   constricting the branch passage at the constriction on-time.